record(r) → antiDupeWindow → pending queue (ConcurrentLinkedDeque)
                                    ↓ (flush every 5s × 20 ticks or when batchSize=500 is reached)
                           TransactionLogFlusher thread
                                    ↓
                      ┌────────────────────────────────┐
                      │  insertBatch dao (File/MySQL)        │
                      └────────────────────────────────┘
                                    ↓
                           DailyJsonLogWriter

CREATE TABLE IF NOT EXISTS vault_transactions (
  id BIGINT AUTO_INCREMENT PRIMARY KEY,
  tx_id VARCHAR(64) UNIQUE,
  serial BIGINT UNIQUE,
  ts TIMESTAMP,
  tx_type VARCHAR(32),
  currency_id VARCHAR(32) DEFAULT 'default',
  from_uuid CHAR(36),
  to_uuid CHAR(36),
  amount DECIMAL(19,4),
  world_name VARCHAR(64),
  metadata_json TEXT
);

{"txId":"...","serial":42,"txType":"PLAYER_PAY","from":"...","to":"...","amount":100.0,...}

CREATE TABLE IF NOT EXISTS vault_charge_requests (
  id BIGINT AUTO_INCREMENT PRIMARY KEY,
  recipient VARCHAR(16),
  sender VARCHAR(16),
  amount DECIMAL(19,4),
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  INDEX idx_vcr_recipient (recipient)
);